The memory system performance with Kaveri under Linux is very poor. Running the stream benchmark (linked below) I only see about 5 GB/s bandwidth. This should be 10-12 on a normal DDR3 system.

With further investigation, it seems that the power management features of the graphics driver are affecting the CPU performance. When I run aticonfig --odgc I see that the GPU DRAM frequency is set to 333 MHz (out of max 667).

However, if I run something compute intensive on the GPU (like ConstantBandwidth from the AMD APPSDK examples), the GPU memory frequency increases to 667. When I run the stream benchmark while the GPU is in high-performance mode I see the expected throughput (~10 GB/s).

Unfortunately, when I try to manually set the GPU memory frequency with aticonfig it tells me that my adapter is unsupported. "ERROR - ATI Overdrive(TM) is not supported on Adapter 0 - AMD Radeon(TM) R7 Graphics

Additionally, I did not see this problem with in Windows.

Motherboard or System Make & Model

Gigabyte GA-F2A88XM-D3H

Applications and Games

Confirmed with the stream benchmark (http://www.cs.virginia.edu/stream/) and other workloads.

Motherboard BIOS Version

Fb6

System Memory Type & Amount

Kingston. 1333 MHz 16 GB in 2 DIMMs

Additional Details

I ran the same benchmark in Windows and saw about double the performance from Linux.